Oxygen breathing bugs older than thought

Toronto, Oct 20 (IANS) Oxygen-breathing bugs thrived on land 100 million years earlier than estimated, according to the latest evidence unearthed by scientists.

The most primitive form of aerobic respiring life on land came into being 2.48 billion years ago, the researchers found.

The research team, led by University of Alberta geomicrobiologist Kurt Konhauser, found this by probing a link between atmospheric oxygen levels and rising concentrations of chromium in the rock of ancient sea beds.

They suggest that the jump in chromium levels was triggered by the land-based oxidation of the mineral pyrite.

Pyrite oxidation is driven by bacteria and oxygen, reports the journal Nature.

Aerobic bacteria broke down the pyrite, which released acid at an unprecedented scale.

The acid then dissolved rocks and the soil into a cocktail of metals, including chromium, which was transferred to the ocean by the runoff of rain water, according to a statement from the university.

The key to the process is oxygen in Earth’s atmosphere that allowed bacterial oxidation of pyrite, Konhauser said.

The researchers dated the peak for chromium levels in marine sedimentary rock to 2.48 billion years ago.

“This gives us a new date for the Great Oxidation Event, the time when the atmosphere first had oxygen,” Konhauser stated.

The same bacterial life forms are alive and well today, living off pyrite and settling in the highly acidic waste waters of mining sites the world over.